//输入两个递增排序的链表，合并这两个链表并使新链表中的节点仍然是递增排序的。 
//
// 示例1： 
//
// 输入：1->2->4, 1->3->4
//输出：1->1->2->3->4->4 
//
// 限制： 
//
// 0 <= 链表长度 <= 1000 
//
// 注意：本题与主站 21 题相同：https://leetcode-cn.com/problems/merge-two-sorted-lists/ 
// Related Topics 递归 链表 👍 247 👎 0


package leetcode.editor.cn;

import com.leetcode.utils.ListNode;

//Java：合并两个排序的链表
public class HeBingLiangGePaiXuDeLianBiaoLcof {
    public static void main(String[] args) {
        Solution solution = new HeBingLiangGePaiXuDeLianBiaoLcof().new Solution();
        // TO TEST
        ListNode l1 = new ListNode(2);

        ListNode l2 = new ListNode(1);

        ListNode result = solution.mergeTwoLists(l1, l2);
        System.out.println(result.val);
    }
    //leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode result = null, temp = null, p1 = null;
        while (l1 != null || l2 != null) {
            if (l1 != null && l2 != null) {
                if (l1.val <= l2.val) {
                    temp = l1.next;
                    if (p1 == null) {
                        p1 = l1;
                    } else {
                        p1.next = l1;
                        p1 = l1;
                    }
                    l1.next = null;
                    l1 = temp;
                    if (result == null) {
                        result = p1;
                    }
                } else {
                    temp = l2.next;
                    if (p1 == null) {
                        p1 = l2;
                    } else {
                        p1.next = l2;
                        p1 = l2;
                    }
                    l2.next = null;
                    l2 = temp;
                    if (result == null) {
                        result = p1;
                    }
                }
            } else if (l1 == null) {
                if (result == null) {
                    result = l2;
                } else {
                    p1.next = l2;
                }
                break;
            } else if (l2 == null) {
                if (result == null) {
                    result = l1;
                } else {
                    p1.next = l1;
                }
                break;
            }
        }
        return result;
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}
